Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$133.69	7.609%	$143.8625	$143.86	$143.85	$143.90
Purchase #2	$127.78	11.443%	$142.4019	$142.40	$142.40	$142.40
Purchase #3	$190.36	10.769%	$210.8599	$210.86	$210.85	$210.90
Purchase #4	$158.31	13.490%	$179.666	$179.67	$179.65	$179.70
Purchase #5	$228.82	11.255%	$254.5737	$254.57	$254.55	$254.60
Purchase #6	$113.66	11.721%	$126.9821	$126.98	$127.00	$127.00
Purchase #7	$201.93	6.264%	$214.5789	$214.58	$214.60	$214.60
7 purchase totals =	$1,154.55		$1,272.9250	$1,272.92	$1,272.90	$1,273.10